Kitchen Extension Cost & Prices 2021

Extending the kitchen area to create a large, wide open-plan space is extremely popular. Open plan living provides space to express oneself as well as creating a more flexible and multi-purpose space for family living. 

In terms of home value, kitchen extensions will add as much value to a home as any type of extension, if not more. You’re talking about 10% of the home’s total value on average, extending up to some 25% in some cases. 

Extending the kitchen is an excellent way to add space to any home, especially if extending into otherwise unused or unwanted space, e.g. a side alleyway or garage.

This article will review the cost of building a kitchen extension, factors that affect the cost and other common questions surrounding kitchen extensions.

Average Cost of Kitchen Extensions Per m²

By analysing 6 primary sources and 5 secondary sources, we discovered these average costs for kitchen extensions. The costs are broken down with the cost of the extension and the kitchen itself. Projects are based on 20m² kitchen extensions (4m x 5m). 

Prices include basic kitchen fittings/relocation of existing kitchen appliances and worktops, etc.

Side return extensions will likely be smaller (around 10m²). 

Type of ExtensionBudget (Per m²)Mid-Range (Per m²)High-End/London and South East (per m²)
Rear or Other Single-Storey £1,450 - £1,800£1,550 - £2,500£2,200 - £4,000
Rear or Other Single-Storey £1,450 - £1,600£1,550 - £2,000£2,200 - £4,000
Garage Extension£1,550 - £1,800£1650 - £2250£2,200 - £4,000
 

Total Cost of Kitchen Extension

Type of ExtensionTotal Cost for Small 10m² Kitchen ExtensionTotal Cost for Small 20m² Kitchen Extension
Rear or Other Single-Storey £14,000 - £40,000£29,000 - £80,000
Rear or Other Single-Storey £14,000 - £40,000£29,000 - £80,000
Garage Extension£15,000 - £40,000£31,000 - £80,000

The lowest average for a smaller 10m² house extension is around £25,000. A large 20m² extension will likely cost in excess of £50,000 or so. This is with basic kitchen fittings only and not more involved interior design and new fittings. 

Kitchen Extension Extra Costs

Much of the costs of extending a kitchen are additional to the basic extension, especially if homeowners are looking to redesign the entire space. Here are some typical extra kitchen extension costs.

Upgrade/ExtraBudget to Mid-RangeMid-Range to High-End
Entire New Kitchen+ £10,000 - £25,000 to extension cost + £12,000 - £50,000 to extension cost 
Quartz Worktops£1000 - £1,300£1,6000 - £2,000+
Orangery or Lantern Roof£5,000 - £10,000£10,000 - £20,000+
Skylight/Velux Window£800 - £1,000£1,000 - £2,000+
Bifold Doors£5,000 - £8,000£7,000 - £12,000

Kitchen Extensions: Not Just a Regular Extension

Kitchen extensions, by default, are single-storey extensions. That means they only cover the downstairs section of the home, except in some exceptional cases in multi-storey houses or flats.

Many people wish to extend their kitchen to create a wide, open-plan downstairs space that opens up the kitchen as a dining room, or even an additional seating area/living room. Most kitchens are already placed at the rear of the house, facing out towards a garden or patio, which makes them straightforward to extend outwards. This also often means that kitchen extensions do not require Planning Permission. 

In the process of extending a kitchen, the kitchen itself is usually replaced, moved or at least modified. This may not be necessary if there’s a long wall to knock and extend, in which case the kitchen can be left intact. 

Another popular choice for kitchen extensions is to create an orangery, which is a conservatory-like space with a lantern skylight window. This creates an open-plan kitchen-dining space with tons of natural light, also opening straight out into the garden via large or bi-fold doors.

Benefits of Kitchen Extensions 

  • Open up significantly more ground floor space
  • More kitchen space
  • Create a genuine kitchen-diner space for cooking, mealtimes and hosting 
  • Extend into the garden with large bi-folding doors to create a large, bright open space
  • Potential for orangery-style skylit or lantern roof  
  • Make use of unused space, e.g. garage space, utility rooms, alleyways and side returns 

Will a Kitchen Extension Add Value to My Home?

Any type of house extension will add value to a property, but this differs depending on the quality of the extension and the location of the property. For example, extensions in some parts of the UK, especially London, can add crazy value to a home. 

A 25m² extension in Kensington and Chelsea might add some £500,000 to a home, according to the ONS. Similarly, Nationwide found that extended 3-bed semis might be worth as much as 23% more. 

In terms of kitchens specifically, 87% of property experts agree that new kitchens add value to a home and they can add some 5% to 15% onto the value of a home.

Kitchen extensions represent an excellent investment for your home and are likely to pay for themselves out of any sales price, provided they are of good quality. 

Kitchen Extension Options

There are several ways to extend the kitchen, some are more likely to suit certain homes than others:

1: Side Return Extension

Many houses, particularly terraced city houses, have an unfilled section at the rear of the property, and also possibly an alleyway. This unfilled section can be filled in, adding space to the kitchen at the rear of the house.

If there’s an alleyway, this can also be filled in, but this might create the need for a Party Wall Act agreement if the extension creates a shared wall with a neighbour.  

2: Single-Storey Rear Extension 

Single-storey extensions are any ground floor extensions, but it’s highly likely that a kitchen extension will extend to the rear of the home into the garden.

This is ideal for extending the kitchen towards the patio or garden, thus creating the potential for an open-plan space that ‘brings the outdoors in’. Also popular for adding skylight or orangery roofs to the new kitchen-dining space. 

3: Wrap-Around Extension

The wrap-around extension is essentially a combination of the aforementioned extensions. The new space will wrap around the house in the form of an alleyway or side return extension, then also extending out into the garden in what will probably be an L-shape. 

4: Garage Extension 

It may also be possible to extend into a garage or utility room. Garages are obviously large spaces, so this could add vast space to any ground floor, though it would likely require significant rearrangement to make it work. 

Planning Permission for Extensions

Kitchen extensions will not always require Planning Permission and may come under Permitted Development.

Permitted Development gives the right for homeowners to extend their property without Planning Permission, so long as they comply with certain conditions. 

Specific limitations apply to homes in: 

  • Conservation Areas
  • Areas of Outstanding Natural Beauty
  • World Heritage Sites
  • National Parks
  • Listed buildings

A key point to bear in mind is that Permitted Development applies only to the ‘original fabric of the building’. If a home has already been extended before then you don’t have the right to extend even more under PDRs – only up to your original quota under PDRs.

The relevant rules to kitchen extensions are: 

For all extensions:

  • Only half the property’s land can be covered by extensions
  • Cannot be higher than the original roof or 3m within 2m of a boundary 
  • Mustn’t alter the roof
  • Must not extend beyond the front of the house

For side extensions: 

  • Cannot exceed 4m
  • Single storey only
  • Only up to half with the width of the original house 

For single-storey extensions:

  • Cannot extend beyond the rear wall by more than 4m for detached or 3m otherwise 
  • Cannot exceed 4m in height

Following a special consultation scheme with neighbours (not the same as Planning Permission), It’s possible to extend further, by: 

  • Over 4 and up to 8 metres for detached houses
  • Over 3 and up to 6 metres for all other houses

Always contact your Local Planning Authority if you’re unsure. Consult your architect and builder – they will be able to tell you if your plans require Planning Permission or not. 

Building Regulations

Kitchen extensions of all kinds will also need to comply with Building Regulations which specify standard rules for everything from fire and electrical safety to proper ventilation. Your contractor should talk you through the Building Regulations process

How Long Do Kitchen Extensions Take?

20m2 extensions will likely take around 2 months, but more complex jobs might take up to 6 months, especially if there are major changes to the plumbing and heating. The duration depends on the complexity and size of the job, the need for groundworks and levelling, access and the weather. 

How to Choose a Kitchen Extension Contractor 

Always opt for a reputable builder with a strong local portfolio.

It’s important to note that the contractor that extends your home may not be the same as the contractor that fits the new kitchen. If they cannot do the work themselves, it’s likely that they will collaborate with a kitchen installer.

Choosing a builder who is part of the Federation of Master Builders (FMB) guarantees builders of a certain independently-verified standard.

Discuss the following with your builder:

  • Itemised quotes and accurate cost breakdowns
  • The expected duration of the job
  • Working hours, waste disposal and noise 
  • Possibility of independent arbitration in the event of a dispute

Get Prices on Kitchen Extensions Near You

We’ve done our best to give you a good idea of what you can expect to pay for a kitchen extension.

However, our guides are not a substitute for a fixed quote specifically for you.

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